Pumping device



Mh 7, H967 J. A. RODDER PUMFING DEVICE Filed Sept. 2, 1,965V

INVENTOR.

Lfffmf @Mfg Bmx@ United States Patent O 3,3tl2,363 PUMNNG DEVICE .lerorne A. Redder, 775 Sunshine Drive, Los Attos, Calif. 94022 liiiled Sept. 2, i965, Ser. No. 434,675 6 Ciaims. (Cl. 23d- 83) This invention relates to liquid-displacement pumps and, more specifically, to improvements in the so-called Toepler pump in which a pool of liquid, such as mercury, is used to transfer gas from one volume to another through a check valve connected between the two volumes. This is a continuation-impart of co-pending U.S. application Serial No. 369,683, filed May 25, 1964, now abandoned.

The check valve closure element used in conventional Toepler pumps is made of a heavy material which has a specific gravity greater than that of the actuating liquid, eg., mercury, and it has a relatively long shaft of lighter material guided through a sleeve to help the liquid lift the closure element and keep the element in line with the valve seat. This heavy and awkward construction limits the speed at which the pump can be operated through its pumping cycle and provides a relatively large surface area on which gas is trapped.

Toepler pumps are well suited for quantitatively transferring gas from one volume to another. However, one disadvantage of conventional Toepler pumps is that they are relatively slow because the mass of liquid used to transfer the gas must be moved slowly to avoid damage to the check valve and other parts of the pump, which ordinarily are made of glass. The liquid is usually mercury because it is relatively inert, inexpensive, has low vapor pressure, and is liquid over a convenient range of temperature. Other suitable liquids may be used, such as gallium, organic liquids, or even water, provided such liquids do not react with the Vgas transferred or have unduly high vapor pressures at the operating temperatures of the pump. However, mercury is most commonly used and is referredto throughout the description of this invention as the operating liquid.

Another disadvantage of conventional Toepler pumps is that its eihciency is impaired by the trapping of gas on the relatively large surface of the check valve used prior to this invention.

Briefly, this invention provides an improved liquiddisplacement pump in which the actuating liquid can be surged back and forth farther than in previous pumps, thereby pumping faster and without damage to the pump. Moreover, the check valve has a minimum surface area to reduce gas trapping and improve pump eiciency. A pumping chamber having an outlet is connected by a conduit to a reservoir which yholds a pool of liquid, such as mercury. Means are provided for causing mercury to iiow through the conduit back and forth between the reservoir and the pumping chamber to alternatively displace gas in the pumping chamber out the outlet, and then create a vacuum in the pumping chamber to admit gas through an inlet tube `which opens into the pumping chamber. Suitable inlet and outlet valving is provided in the pumping chamber outlet in the inlet tube for controlling the iiow of mercury and gas through the pumping chamber in response to the flow of mercury in and out of the chamber. p

Preferably, the inlet tube opens into `the pumping chamber at a location horizontially spaced from where the conduit opens into the pumping chamber from the reservoir. With this construction, the inlet tube, which ordinarily is made of glass, is located out of the path of mercury which may enter the pumping chamber through the conduit at a relatively high velocity.

Preferably, the pumping chamber has a lower portion of smaller cross-sectional area than the upper-portion of the reservoir, and the pumping chamber is mounted on top of the reservoir and disposed to extend a slight distance down into it. A conduit of smaller diameter than the lower portion of the pumping chamber extends from the bottom of the pumping chamber to a point adjacent the reservoir bottom. Thus, when the reservoir is substantially full of a pool of mercury, the level of mercury is such that the lower portion of the pumping chamber overlying the conduit is covered with mercury and forms a surge pool to reduce the tendency of mercury to jet into the pumping chamber during the early part of the cycle when the pumping chamber is being filled with mercury. This reduces splashing, which might trap gas being pumped or which might damage the pump.

Preferably, the inlet tube opens near the bottom of the pumping chamber and carrie-s a check valve located relatively close to the bottom of the pumping chamber so as mercury rises in the pumping chamber, the check valve is forced shut at an early stage to minimize the back flow of gas out of the inlet tube.

A check valve is preferably mounted in the pumping chamber outlet to permit the exit of gas from the pumping chamber and to prevent its reentry as the mercury is removed from the pumping chamber.

In the presently-preferred forni of the invention, the valve in the pumping chamber outlet is a liquid-sealed Check valve which includes a hollow cage with a first opening and a second opening located above the first. An annular seat is disposed around the first opening to face toward the second opening in the cage. A ball is disposed in the cage, and is of such a diameter as to be adapted to rest on the annular seat and close it when liquid is withdrawn from the pumping chamber. A housing is disposed around the cage to hold a pool of liquid at a level above the annular seat. Thus, when liquid is forced into the pumping chamber, it eventually reaches the check valve and the outlet and forces gas past the check valve and some liquid into the housing surrounding the cage. As liquid is removed from the pumping chamber, some eX- cess liquid in the housing surrounding the valve cage flows from the housing through the cage, and past the ball and through the iirst opening back into the pumping chamber. The current of liquid sweeps the ball from the open position to a closed position against the annular. seat, an-d the ball is held submerged under the pool of mercury held around the cage bythe housing.

The pressure on top of the ball is suiiiciently great to hold the ball down in a closed position, even though it might be less dense than the surrounding mercury. That is one of the major advantages of the preferred check valve of this invention, because it permits the use of relativelylight weight check balls so that mercury can be surged more rapidly through the valve without damage to the parts.

Preferably, the ball is of a ceramic material lighter than the liquid, and the annular seat around the rst opening in the cage is carefully ground to match the curvature of the ball and achieve a good seal.

Although notentirely critical, best sealing results are obtained when the tangent to the ball at the point where it makes contact with the annular seat forms an angle of about 55 to 65 to the horizontal, an angle of 60 being preferred.

Preferably, retaining means, such as a cross bar, is disposed above the second opening in the cage to prevent the ball from being driven out of the cage as mercury flows through it.

` These and other aspects of the invention will be more fully understood from the following detailed description and the accompanying drawings, in which:

FIG. 1 is a sectional elevation of the presently-preferred embodiment of the pump;

FIG. 2 is a view taken on line 2-2 of FIG. l; and

FIG. 3 is a schematic drawing of an alternate form of a check valve in the outlet of the pumping chamber.

Referring to the drawing, a hollow pumping chamber has a bottom 11 which is of slightly smaller cross-sectional area than the upper portion of a reservoir 12. The bottom of the pumping chamber extends slightly into the upper end of the reservoir and is sealed yto it. A vertical conduit 13 opens at its upper end into the central portion of the bottom of the pumping chamber and opens at its lower end into the reservoir adjacent the reservoir bottom. A supply line 14 connects the upper portion of the reservoir through a stop cock 15 and a three-way solenoidactuated valve 16 to either the atmosphere through a line 17 or a vacuum pump 18 through a line 19. As shown in the drawing, the solenoid valve is set to connect the line 14 to the vacuum pump. In this condition, a pool of mercury 20 in the reservoir is at a maximum level 21 which also covers the lower portion lof the bottom of the pumping chamber. With the mercury in this position, the pump is ready to begin a displacement stroke to force gas out of the pumping chamber. This is achieved when the solenoid valve is actuated (as viewed in FIG. l) by conventional automatic circuitry (not shown) to admit atmospheric pressure into the reservoir and force mercury up conduit 13 into the pumping chamber which is at a pressure substantially less than atmospheric.

Gas to be pumped is admitted into the pumping chamber through a horizontal inlet tube 22 which opens into the lower portion of the pumping chamber and terminates in a downwardly extending leg 23 just above the maximum level 21 of mercury .in the pumping chamber. An inlet check valve 24 is mounted in the lower end of the leg 23 of the inlet tube, and it includes a ceramic ball 25 of a density lower than mercury. With the level of the mercury in the position shown in FIG. l, the ball 25 rests on a glass cross rod 26 secured across the lower end of leg 23. The cross rod prevents the ball from falling out of the inlet tube leg, but neither it nor the ball closes the leg against the ow of gas from a source 28. A downwardly facing annular ground glass seat 29 receives the ball as mercury rises in the chamber during the operation of the pump to close the inlet check valve. Longitudinal slots 3i) adjacent the end of the lower end of the leg of the inlet tube facilitate the flow of gas from the source around the ball and into the pumping chamber which is at a pressure lower than the gas source. A control valve 31 in the inlet tube 22 controls the ow of gas sample from the source to the pumping chamber.

A safety check valve 31A is mounted in the inlet tube 22 to prevent damage to the pump if control valve 31 is opened to the atmosphere. The safety check valve includes an annular valve seat or restriction 31B, a retaining rod 31C extending into the line upstream from the seat, and a ball 31D in the tube between the seat and the retaining rod. The ball is of such a Weight that it does not seat when gas flow past it is slow, but as gas flow approaches a value which would damage the pump, the ball is forced against the seat. In one form, the ball completely seals. Preferably, the ball and seat are designed to permit gas to flow slowly past them when the ball is seated. In one form, the ball and seat do not make a perfect seal so that gas can leak past them at a rate which is low enough to avoid damage to the pump. In another form, the ball has a plurality of holes 31E through it which permit gas to seep into the pump at a rate which cannot cause damage.

A similar safety check valve 31F is installed in supply line 14 to limit the rate of air flow into the reservoir and thus protects the pump from excessive gas flow. The construction and operation of check valve 31F is identical 4f with that just described for safety check valve 31A and is not repeated for brevity.

An annular partition 32 across the upper end of the pumping chamber forms an outlet 33 around which is sealed an upright tubular cage 34 having an opening 35 at its lower end and an opening 35A at its upper end. A downwardly and inwardly inclined annular seat 37 is formed around the rst or lower opening 35 to receive a ceramic valve ball 36, which has a specic gravity of less than that of mercury. Preferably, the annular seat 37 is carefully ground glass so that it forms an angle of 60 with the horizontal. Experience has shown this is the best sealing results obtained with this construction, although the angle can be varied between about 55 and about 65.

A plurality of vertical slots 38 are formed in the sides of the cage and extend from the upper end of the cage down to a point just above the upper portion of the ball 36 when seated.

An upright, generally cylindrical housing 40 is sealed at its lower end to the pumping chamber to surround the cage. A cross bar 41 is secured across the interior of the housing just above the cage to prevent the ball from being driven from the cage as mercury ows upwardly through the outlet valve during the exhaust portion of the pumping cycle. With the solenoid valve set as shown in FIG. l, a pool of mercury 42 is held in the housing around and in the cage to a lower level 43. When the solenoid valve is turned to admit atmosphere to the reservoir, mercury flows up through the pumping chamber and into the cage to ll the housing with mercury to an upper level 44. At this point, the valve ball 36 4rises to the dotted line position shown in FIG. l and bears against the underside of cross bar 41.

A bulbar sample receiver 46 is sealed at its lower end through a connecting tube 47 to the upper end of the housing. An index mark 48 is used for taking an accurate reading of the gas trapped in the sample receiver. Gas can be exhausted from the sample receiver through an exhaust line 50 connected to the upper end of the sample receiver, and a stop cock 51 which vents line 50 to the atmosphere.

The lower end of monometer tube 52 is connected by a tube 53 to the lower portion of the housing below the lower operating level of mercury in the housing. The lower end of the monometer is connected through a tube 54 to the lower end of a secondary reservoir 55 which holds a pool of mercury 56. The upper portion of the secondary reservoir is connected through a conduit 57 by a three-way valve 58 to either atmospheric pressure or a source of vacuum (not shown). A stop cock 59 in tube 54 controls the rate of flow of mercury to and from the reservoir. A valve 60 in a branch tube 61 connected to tube 53 permits the monometer and housing to be connected to a vacuum source (not shown) for the purpose described below.

In operating the pump shown in the drawings, the pumping chamber, which is assumed full of mercury from preceding operation, is evacuated by turning solenoid valve 16 to connect at the main reservoir 12 to the vacuum pump. Valve 31 in the inlet tube is closed, and so is stop cock 51 in exhaust line 50 above the sample receiver 46. The mercury in the main reservoir rises to the maximum level 21, and the pumping chamber is now evacuated. Three-way valve 58 is turned to connect the secondary reservoir to vacuum, and stop cock 59 is opened slightly to allow any mercury in the housing and monometer to drain to a mark 63 on the tube 54 just above stop cock 59, which is then closed. Valve 60 is opened to evacuate the sample receiver and monometer, and is then closed.

Three-way valve 58 is turned to admit atmospheric pressure into the top of the secondary reservoir 55. Stop cock 59 is opened slightly, and mercury is allowed to rise from the secondary reservoir until it reaches level 43 in the housing surrounding the cage at the outlet end of the pumping chamber. The mercury stands at the same level in the monometer. Stop cock 59 is then closed.

Valve 31 is opened, and gas from the gas source 28 ows in through inlet tube 22 and inlet check valve 24. After the pressure in the pumping chamber is substantially equal to that of the gas source, solenoid valve 16 is actuated (as shown in FIG. l) to admit atmospheric pressure into the reservoir. The gas source 23 is at a pressure substantially below atmospheric, and therefore mercury is forced from the reservoir up conduit 13 and into the pumping chamber. The layer of mercury initially present in the pumping chamber reduces the tendency of mercury to squirt or geyser into the pumping chamber, thereby minimizing the amount of gas which might otherwise be trapped by a turbulent stream of mercury. Moreover, the inlet valve and leg being horizontally displaced from the upper end of the conduit 13 permits the inlet check valve to be relatively close to the bottom -of the pumping chamber without any danger of damage due to mercury surging into the pumping chamber through conduit 13. The rate at which -air enters the reservoir is controlled by the position of stop cock 15. As the mercury level rises in the pumping chamber, the ball in the inlet valve floats up against the annular inlet seat in the downwardly extending leg of the inlet tube and prevents mercury from traveling toward the gas source.

As the pumping chamber fills, the pressure of the gas above the rising mercury increases to a value sucient to lift the ball in the outlet valve and permit gas to escape from the pumping chamber into the housing. The mercury in the pumping chamber continues to rise and flow through the outlet valve until it reaches the level 44 in the housing. At this point, the solenoid valve 16 is returned to the position shown in FIG. 1 so that vacuum is -applied to the reservoir causing the mercury in the housing to flow through the cage and down the outlet check valve. The ceramic check ball in the outlet valve, which had risen to the dotted line position shown in FIG. 1, is swept by the stream of mercury pouring down through the vertical slots 38 in the cage against the annular seat 37 just as the mercury in the housing reaches level 43 shown in FIG. 1. The mercury in the pumping chamber continues to fall so that the head of mercury remaining in the housing is suiiicient to hold the ball 36 down on the annular seat, even though the ball is of lower specic gravity than the mercury. This permits the mercury to be surged relatively rapidly through the Valve without damage to the equipment.

The foregoing cycle is repeated, preferably automatically, as often as necessary until the desired amount of gas is flowed from the gas source into the sample receiver.

After the appropriate amount of gas is pumped into the sample receiver, atmospheric pressure is admitted through valve 58 to the secondary reservoir. Stop cock 59 is opened slightly to permit mercury to rise to the index mark 48 below the sample receiver. Since the monometer tube 52 was fully evacuated, the mercury rises in it to a level 62, which is above line 48. The difference between the level of the mercury at line 48 and the level of the mercury in the monometer tube is the measure of the gas pressure in the sample receiver. The volume of sample receiver is accurately known, so the quantity of gas lcan readily be determined. The gas in the sample receiver may be exhausted through valve 6@ and branch tube 61 when the monometer and housing are evacuated as previously described. The pump is now ready to transfer another sample.

FIG. 3 shows a simplified control check valve 64 which includes a ceramic spherical check ball 65 disposed on an annular seat 66 in a vertical tube 67 which connects the lower end of a housing 68 with the upper end of the pumping chamber 10. The ball and seat are of construction identical with that described in FIG. 1 and, therefore,

d not repeated for brevity. A horizontal retaining rod 69 is mounted across the housing above the ball and spaced from it to permit mercury to lift the ball from the seat, and yet prevent the ball from leaving the immediate vicinity of the seat.

The pump with a check valve shown in FIG. 3 is operated in a manner similar to that described for the pump shown in FIG. 1. During the exhaust stroke, mercury hows up from the pumping chamber, lifts the ball oif the seat, and the mercury continues to rise to or above retaining rod 69. The inlet stroke for the pumping chamber is begun by lowering the mercury level, causing mercury to flow throu-gh the tube 67 and sweep the ceramic ball on to the annular seat. Although the ceramic ball is of density less than the mercury, the weight of the mercury on the ball holds it rmly seated.

l claim:

1l. A liquid displacement pump comprising a reservoir for holding a pool of liquid, a pumping chamber having an outlet, a conduit connecting the pumping chamber to the reservoir, means for causing the liquid to flow through the conduit back and forth between the reservoir and the pumping chamber between a low and a high position in the chamber, an inlet tube opening into the pumping chamber at a location horizontally spaced from where the conduit opens into the pumping chamber and above the liquid in the low position in the chamber, a check valve in the inlet tube adjacent the end of the tube opening into the pump chamber, and a check valve in the pumping chamber outlet.

2. A liquid displacement pump comprising a reservoir for holding a pool of liquid, a pumping chamber having an outlet, the pumping chamber being disposed over the reservoir and having a lower portion which fits down into an upper portion of the reservoir, a conduit conecting the pumping chamber to the reservoir, a supply line opening into the reservoir above the lower portion of the pumping chamber through which pressure on the liquid in the reservoir can be varied to cause the liquid to flow through the conduit back and forth between the reservoir and the pumping chamber between a low and a high position in the chamber, an inlet tube opening into the pumping chamber -at a location horizontally spaced from where the conduit opens into the pumping chamber and above the liquid in the low position in the chamber, a check valve in the inlet tube adjacent the end of the tube opening into the pump chamber, and a check valve in the pump-in g chamber outlet.

3. A liquid displacement pump comprising a reservoir for holding a pool of liquid, a pumping chamber having an outlet, the pumping chamber being disposed over the reservoir and having a lower portion which fits down into an `upper portion of the reservoir, an upright conduit of smaller cross-sectional area than the lower portion of the pumping chamber connecting the pum-ping chamber to the reservoir, a supply line opening into the reservoir above the lower portion of the pumping chamber by which pressure on the liquid in the reservoir can be varied to cause the liquid to flow through the conduit back and forth between the reservoir and the pumping chamber between a low and a high lposition in the chamber, an inlet tube opening into the pumping chamber at a location :horizontally spaced from where the conduit opens into the pumping chamber and above the liquid in the low position in the chamber, a check valve in the inlet tube adjacent the end of the tube opening into the pump chamber, and a check valve in the pumping chamber outlet.

fi. A liquid displacement pump comprising a reservoir for holdin-g a pool of liquid, a pumping chamber having an outlet, a conduit connecting the pumping chamber to the reservoir, means for causing the liquid to ow through the conduit back and forth between the reservoir and the pumping chamber between a low and a high position in the chamber, an inlet tube opening into the pumping chamber lat a location horizontally spaced from where the conduit opens into the pumping chamber and adjacent the bottom of the pumping chamber, a check valve in the pumping chamber outlet, and a check valve in the inlet tube adjacent the bottom of the pumping chamber.

5. A displacement pump comprising a reservoir, a pool of liquid in the reservoir, a pumping chamber ccnnected to the reservoir and having an outlet and an inlet, a check valve in the inlet, a check valve in the outlet, the Outlet check valve including an yannular seat disposed in the pumping chamber outlet and facing upwardly, a spherical ball `disposed on the seat, the ball being of a diameter to rest on the annular seat and close it, the ball being of less specific gravity than the liquid, means for causing the liquid to flow from the reservoir into the pumping chamber to a level above the annular seat and back to the reservoir to `a level below the annular seat and below the pumping chamber inlet, and retaining means spaced from the ball to limit its travel from tne seat.

6. A displacement pump comprising a reservoir, a pool of mercury in the reservoir, a pumping chamber connected to the reservoir and having an outlet and an inlet, a check valve in the inlet, a check valve in the outlet, the outlet check valve including an annular seat disposed in the pumping chamber outlet and facing upwardly, a spherical ceramic ball disposed on the seat, the ball being of a specific gravity less than that of mercury and of a diameter to rest `on the annular seat and close it, means for causing the mercury to ow from the reservoir into the pumping chamber to `a level above the annular seat and back to the reservoir to a level below the annular seat and below the pumping chamber inlet, and retaining means spaced from the ball to limit its travel from the seat.

References Cited by the Examiner UNlTED STATES PATENTS 1,380,415 6/1921 Putnam 137-533.11 1,555,934 10/l925 Barker 137-533.11 2,233,818 3/1941 Matter 137-513 2,258,415 itl/1941 Lago 230-83 2,427,764 9/1947 Carson 137-513 2,620,961 12/1952 Balhouse 23S-83 2,725,074 11/1955 McLeod 137-513 2,902,208 9/1959 Hanin 230-83 FOREIGN PATENTS 490,316 2/1953 Canada.

DONLEY J. STOCKlNG, Primary Examiner.

WARREN E. COLEMAN, HENRY F. RADUAZO,

Examiners. 

1. A LIQUID DISPLACEMENT PUMP COMPRISING A RESERVOIR FOR HOLDING A POOL OF LIQUID, A PUMPING CHAMBER HAVING AN OUTLET, A CONDUIT CONNECTING THE PUMPING CHAMBER TO THE RESERVOIR, MEANS FOR CAUSING THE LIQUID TO FLOW THROUGH THE CONDUIT BACK AND FORTH BETWEEN THE RESERVOIR AND THE PUMPING CHAMBER BETWEEN A LOW AND A HIGH POSITION IN THE CHAMBER, AN INLET TUBE OPENING INTO THE PUMPING CHAMBER AT A LOCATION HORIZONTALLY SPACED FROM WHERE THE CONDUIT OPENS INTO THE PUMPING CHAMBER AND ABOVE THE LIQUID IN THE LOW POSITION IN THE CHAMBER, A CHECK VALVE IN THE INLET TUBE ADJACENT THE END OF THE TUBE OPENING INTO THE PUMP CHAMBER, AND A CHECK VALVE IN THE PUMPING CHAMBER OUTLET. 